


fly on the wall.

by orphan_account



Category: Undertale (Video Game)
Genre: Darkfic, Fontcest, Incest, M/M, Masturbation in Shower, Non-Consensual Voyeurism, Pillow Grinding, Rape, Sans is truly fucked up, Sibling Incest, bad brother au, wax poetic: first attempt
Language: English
Status: Completed
Published: 2018-03-19
Updated: 2018-03-19
Packaged: 2019-04-04 18:48:18
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Rape/Non-Con
Chapters: 1
Words: 894
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14026467
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: As disjointed as it is disgusting. No rhyme or reason to what Sans doesn't feel for baby brother.Off the wall, in the walls.





	fly on the wall.

**Author's Note:**

  * For [brittlelimbs](https://archiveofourown.org/users/brittlelimbs/gifts).



> A break from fluff for... some darkfic? Yay? XD  
> I attempted my dear friend Brittlelimbs' style, wax poetic. Hopefully I did it a little bit of justice.  
> Please. Mind the tags.

his brother’s cock is skinny, but it’s veiny with a bulbous head like an orange beret and, comparatively speaking, that thing really snaps into existence at the slightest encouragement.

including pressure from freezing fucking water (the tap in this place only spits out cold or cold but skeletons don’t need showers anyway) as papyrus wrests the handheld showerhead from its notch in the tile and steadies it centimeters from the budding protuberance, it's gotta be that close, sans figures, or else it just piddles over the area and gives papyrus none of the wet friction that he’s seeking (seriously, they’re only paying seven hundred a month and a decent shower experience wasn’t a commodity this shithole had to offer, but bones can and have always been rinsed with a damp towel by the sink so papyrus’ zealous insistence to be SQUEAKY CLEAN! BECAUSE MY BONES FEEL… CHALKY! didn’t fool sans in the slightest) and as his brother bends over gasping and rattling, spreading his legs apart in the tub streaky down the sides like yellowed teeth and steadying himself with his other hand

that’s when sans’ prurience begins to pool in his pelvis.

he noticed the hole in his wall on day one and his brother’s fascination with the showerhead by late afternoon of day two. papyrus ran full-tilt into their new place like a child on moving day and claimed the bigger of the two bedrooms for himself, which realistically speaking was like comparing a broom closet to a toilet stall for size. now sans wouldn't trade his bedroom for the world.

he realized by day three when papyrus attempted nonchalance and headed to the bathroom for an after-breakfast washing up that his baby brother had found a new way to masturbate and, more importantly, that conveniently-placed hole placed sans at the very corner of the tub well within the plastic curtain, very nearly joining papyrus but just on the flip side. that hole was definitely man-made, previous renter perhaps?

small enough to go unnoticed by those who don’t consider such things.

it was a little uncomfortable to get down kneecaps to floorboards, but sans discovered and very quickly grew to appreciate crushing his erection with the palm of his hand against the wall, thrusting into the unforgiving space until he eventually splattered hot cum the color of mouthwash up the peeling pink paper. call it art. papyrus never came in his room anyway.

he likes it because it’s wrong.

he knows it’s wrong

papyrus didn’t know anything, of course, at the beginning. he wholeheartedly believed Big Bro's complaints of nightmares in the underground and that that was why he climbed into bed with him at night. he soother sans’ crocodile tears and in a half-awake stupor he would wrap his arms around him, drawing him close, “shh, brother, it’s okay”. quiet, gentle, for once.

papyrus was a heavy sleeper; sans would tease the vertebrae of his brother's neck with his forked tongue, dipping in and out, leaving thin trails of blue residue that evaporated by morning. that racecar bed was a pinnacle of innocence and therefore irresistibly erotic, so when papyrus left the house sans would grind his pelvis into his cheerful yellow pillows until the fabric was massaging his newly sprouted, glowing length. he took great pleasure in the knowledge that papyrus would rest his head on it that night.

and then he would stumble to the bathroom, barely able to make it down the hallway as he thrust viciously his hand; streaked the toilet bowl with his shame followed with thick strands of blueberry vomit (because he knew it was wrong).

routine.

he stopped throwing up, like, three years ago.

even when the intrusive thoughts enter his skull, when his brother throws his arms around him and hugs him and he gets a full-color mental image of snapping his rips in half between his hands, grinding them into powder, just ‘cuz.

papyrus was, maddeningly, and angel and it was just gonna make it so much worse for him. for both of them.

never once did sans believe he wouldn't act on it. a matter of when, not if. maybe it was moving aboveground, maybe it was their decidedly closer quarters, maybe it was just. sans. but sans had another “tearful nightmare” three nights into week two and gladly let papyrus envelop him once again into his arms

now it's month eight and papyrus always starts whining like a baby when he finds his soul pinned to the mattress, the manchild’s still half-asleep but he’s also so astute. there was something so sensual about those jejune pearls of light awakening in papyrus’ crescent moon eye sockets just to find himself peering up at sans. crescents to ferries wheels that first time, now forming new moons, blue moons. 

early morning is just beginning to creep through the filmy lace curtains, a pale blue semigloss of sunlight barely reaching the dark pockets of the room.

H-HI, BROTHER. he’s loud now, even in a whisper, that's 'cuz he's wide awake, CAN’T SLEEP?

you’re blue now. heh. geddit?

papyrus wriggles and yeah, of course he can't move. it's stupidly hot. temperature. YEAH, I GEDDIT.

sans kicks off the duvet and squeezes his brother hard, nuzzling beneath his mandible,

OW, SANS, THAT HURTS,

i love you, ya know that?

And then there's a brief silence, before


End file.
